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supermenscher
Jul6-04, 07:12 PM
1. What is the frequency of the magnetic filed if it is know to be perpendicular to the electric field. The magnetic field is 0.00178T and the electric field is 8000V/m.

2. I just need the angle for this one. At a certain location, the Earth's magnetic field has a magnitude of 5.6E-5T and points in a direction that is 72 degrees below the horizontal. Find the magnitued of the magnetic flux through the top of a desk at this location that measures 110cmX73cm.

I know you used magnetic flux = BAcos theta....but what is the angle theta, I tried 72 degrees and 18 degrees, what angle do I use?


3. When the switch is closed in a RL circuit the current in the circuit increases from 0A to 0.22A in 0.15s. This current also has a resistance of 5.5 ohms. What is the inductance L, how long after the switch is closed does the current have a value of 0.41A, and what is the maximum current that flows in the cirucit.

I have tried this problem using every formula possible and still can't get it...can someone help me out, even to get me started? Thank you.

wisky40
Jul7-04, 02:05 AM
I want to know if in problem 3 you're forgetting the voltage (emf).

wisky40

supermenscher
Jul7-04, 10:00 AM
Yes, sorry the voltage is 9.0V

Gza
Jul7-04, 12:56 PM
I have tried this problem using every formula possible and still can't get it...can someone help me out, even to get me started?


I think your problems start from there. Stop thinking in formulas and start thinking physically. You are given the rate the current changes. Changing current causes a changing magnetic field (Hint: think faraday's law).